1. Field of the Invention
The invention relates to ophthalmic laser treatments, particularly to devices and systems capable of performing multiple ophthalmic photocoagulation treatments.
2. Information Disclosure Statement
Ophthalmic laser treatments comprise a variety of modalities to combat different diseases or indications. Ion or dye lasers, such as Argon and Krypton lasers, have been preferred because the wavelengths they produce (488 or 514 nm for Argon, 648 nm for Krypton) are effective in various photocoagulation procedures. For example, wavelengths produced by Argon lasers are well absorbed in hemoglobin and thus are effective for coagulating hyperproliferating or leaking blood vessels that can occur in diabetic patients, among others. (see U.S. Pat. No. 5,147,349)
U.S. Pat. No. 5,295,989 describes a light cable in an apparatus for ophthalmic treatment consisting of a plurality of optical fibers. A preferred embodiment utilizes an Argon laser beam as a treatment light source.
Many of the current photocoagulators are of an inconveniently and inefficiently high cost, size and complexity. For example, conventional Krypton and Argon lasers are capable of emitting sufficient power levels for photocoagulation but are bulky, technically complex, and are inefficient “(below 0.1%) requiring up to 40 kW of three phase power and associated water cooling” to remove excess heat. (see U.S. Pat. No. 4,917,486) Thus, these setups are expensive and often require fixed installations.
The advantages of using a laser diode over other laser sources are espoused in U.S. Pat. No. 4,917,486, which describes the laser diode as having a relatively low cost (around 10-20%) compared to an Argon laser, high efficiency of around 30% providing sufficient output power with a low amount of electrical input, lack of need for water cooling and smaller size. U.S. Pat. No. 4,917,486 uses infrared light preferably at a wavelength of substantially 800 nm, which is longer than Kr or Ar wavelengths, and preferably emitted by a laser diode.
Other photocoagulation treatment methods include the use of probes for insertion into the eye prior to irradiation, the use of photosensitive substances, whose absorption spectra define the laser wavelength needed in conjunction with photodynamic therapy, and the use of two or more radiation sources simultaneously or during a single treatment to enhance treatment efficacy. Each of these alternatives require more complex procedures and equipment than the simple use of a single wavelength and thus introduce new potential problems into the treatments. They do not address the current treatment modality as does the present invention.
Generally also low energy red lasers, operating wavelengths between 600 and 700 or so nm, are often used as aiming laser beams to guide the higher power laser beam which treat the diseases. These are chosen for this function as these wavelengths are considered easy to see and not likely to induce reactions within the patient. References dealing such lasers are not directly useful to the problems solved herein and are thus excluded.
Ophthalmic treatment systems have been proposed that are capable of performing different types of treatments with a single system or device. However, to achieve different results, these systems must apply radiation at multiple wavelengths, usually through availability of multiple sources. A system that can perform multiple treatment types with a single wavelength range has not been disclosed.
Recent commercial announcements describe a new multi-laser photocoagulation laser system for treating a range of retinal diseases. The system provides a spectrum of green, yellow and red light in a single device and is claimed to be useful for age-related macular degeneration, diabetic retinopathy, diabetic macular edema and other diseases.
Likewise, U.S. Pat. No. 5,331,649 discloses a system for producing different wavelengths often needed in ophthalmic treatments. This is a system for generating a plurality of wavelengths of light in a single apparatus.
U.S. Pat. No. 5,423,798 describes a system for performing laser vitrectomy and endophotocoagulation within a single system to avoid the need to change devices between the two treatments. Two wavelengths can be applied through the same fiberoptic delivery apparatus. The first wavelength for photoablation operates at about the 2.94 micron region, and the second wavelength for photocoagulation operates at about 800 nm. The first photo-ablative laser comprises an Er:YAG crystal and the second photocoagulative laser is a semiconductor laser diode array.
U.S. Pat. No. 5,144,630 describes a wavelength conversion system for use in ophthalmic surgery. The system switches between a plurality of nonlinear crystals to allow for applying radiation with a wavelength range from ultraviolet to infrared and large enough to replace the need for the use of many traditional lasers for a variety of treatments. The ability to switch wavelengths allows one to treat a variety of conditions with one system.
The above patents illustrate the current state of the art with respect to ophthalmic, and especially photocoagulative, laser surgery. Different wavelengths are known to affect various tissue types differently, and thus different wavelengths are thought to be more effective for different treatments. The presence of multiple laser sources increases the base cost and when switching between them, potential new errors or precautions are required in their operation. It would be extremely useful, therefore to provide a laser system operating at a wavelength that is effective for a variety of photocoagulative treatments. The present invention addresses this need.